Hi, Gregory Farnum wrote: > 3) The cost of a cache miss is pretty high, so they should only be > used when the active set fits within the cache and doesn't change too > frequently. Can you roughly quantify how long a cache miss would take? Naively I'd assume it would turn one read into a read from the backing pool, a write into the cache pool, then the read from the cache. Is that right? > So, Ceph will not automatically redirect to the base pool in case of > failures; in the general case it*can't*, but you could set up > monitoring to remove a read-only pool if that happens. But in general, > I would only explore cache pools if you expect to periodically pull in > working data sets out of much larger sets of cold data (e.g., jobs run > against a particular bit of scientific data out of your entire > archive). That's a pity. What would be your hesitation about using WB caching with RBD images, assuming the cache pool is sized large enough to match the working set. Cheers, Dan -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.ceph.com/pipermail/ceph-users-ceph.com/attachments/20140507/1d4d8c03/attachment.htm>
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